Run ROS2 Node

#ros2   #cli   #namespace   #remap  

---

Table of Content

Run ROS2 Node

Run minimal ROS2 node from:

• cli
• add namespace
• remap topic
• remap node name
• launch file
• cli control debug level

Run from cli

ros2 run params_demos minimal
#
[INFO] [1680205241.556490384] [simple_param_node]: my_int: 3
[INFO] [1680205242.543293520] [simple_param_node]: my_int: 2
[INFO] [1680205243.543186445] [simple_param_node]: my_int: 1
[INFO] [1680205244.543174591] [simple_param_node]: close timer

ros2 node list
# 
/simple_param_node

Add namespace

terminal 1

ros2 run params_demos minimal --ros-args --remap __ns:=/custom

terminal 2

ros2 node list           
#
/custom/simple_param_node

Remap topic name

terminal 1

# without namespace
ros2 run params_demos minimal --ros-args --remap /simple_param_node/my_topic:=/new_topic

# with namespace
ros2 run params_demos minimal --ros-args --remap /custom/simple_param_node/my_topic:=/new_topic --remap __ns:=/custom

terminal 2

ros2 node list           
#
/custom/simple_param_node

ros2 topic list 
#
/new_topic

Topic absolute name

topic name start with forward slash are absolute
when you rename topic and the remap topic name are not absolute. namespace add to the topic name as prefix

ros2 run params_demos minimal --ros-args --remap /custom/simple_param_node/my_topic:=new_topic --remap __ns:=/custom

ros2 topic list 
#
/custom_ns/new_topic

ros2 run params_demos minimal --ros-args --remap /custom/simple_param_node/my_topic:=/new_topic --remap __ns:=/custom

ros2 topic list 
#
/new_topic

Add fqn to topic name

Topic and Service name mapping to DDS

fqn = self.get_fully_qualified_name()
self.get_logger().info(f"node name: {node_name}")
self.pub = self.create_publisher(Int32, fqn + TOPIC, 10)

Remap node name

Terminal 1

ros2 run params_demos minimal --ros-args --remap __node:=node_new_name

Terminal 2

ros2 node list
#
/node_new_name

ros2 topic list
#
/node_new_name/my_topic
/parameter_events
/rosout

Remap node name with namespace

Terminal 1

run params_demos minimal --ros-args --remap __node:=node_new_name --remap __ns:=/custom

Terminal 2

ros2 node list 
#
/custom/node_new_name

ros2 topic list
#
/custom/node_new_name/my_topic
/parameter_events
/rosout

Note

name = self.get_name()
ns = self.get_namespace()
fqn = self.get_fully_qualified_name()
self.get_logger().info(f"node name: {name}")
self.get_logger().info(f"ns: {ns}")
self.get_logger().info(f"fqn: {fqn}")

ros2 run params_demos minimal --ros-args --remap __node:=node_new_name --remap __ns:=/custom
[INFO] [1680233355.573926310] [custom.node_new_name]: node name: node_new_name
[INFO] [1680233355.574155685] [custom.node_new_name]: ns: /custom
[INFO] [1680233355.574342657] [custom.node_new_name]: fqn: /custom/node_new_name

launch

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    ld = LaunchDescription()

    sim_node =  Node(
            package='params_demos',
            namespace='custom',
            executable='minimal',
            name='simple_node'
        )


    ld.add_action(sim_node)
    return ld

ros2 node list
/custom/simple_node
#
ros2 topic list
/custom/simple_node/my_topic

remap topics

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    ld = LaunchDescription()

    sim_node =  Node(
            package='params_demos',
            namespace='custom',
            executable='minimal',
            name='simple_node',
            remappings=[
                ("/custom/simple_node/my_topic", "/new_topic_name")
            ]
        )


    ld.add_action(sim_node)
    return ld

ros2 node list
/custom/simple_node
#
ros2 topic list
/new_topic_name

---

cli and launch logging level control

more ros2 logging info

cli

loging level:

• debug
• info
• warn
• error

terminal

ros2 run params_demos minimal --ros-args --log-level debug

launch

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    ld = LaunchDescription()

    sim_node =  Node(
            package='params_demos',
            namespace='custom',
            executable='minimal',
            name='simple_node',
            remappings=[
                ("/custom/simple_node/my_topic", "/new_topic_name")
            ],
            arguments=['--ros-args', '--log-level', 'warn']
        )


    ld.add_action(sim_node)
    return ld

---

Reference

• ROS Command Line Arguments
• Topic and Service name mapping to DDS